Low pressure mixing apparatus for atomizing fluids

ABSTRACT

The liquid feed injector as hereindescribed uses sequential stages of increased severity mixing to fully atomize a liquid portion of a combined liquid and gaseous stream. Sequential mixing consists of a first mild mixing that takes place in a mild mixing zone and blends the liquid and gaseous material into a substantial uniform mixture. The uniform mixture of liquid and gaseous material passes through another stage of vigorous mixing where the liquid is sheared and gas is dispersed throughout the liquid by dividing the mixture into a plurality of small streams and directing the projection of the streams into impingement with an impact medium to produce a homogeneous mixture of fine gas bubbles dispersed in the liquid. The homogeneous liquid and gas mixtures are then discharged through one or more discharge nozzles to effect atomization and distribution of the liquid in a suspension of fluidized solids. The sequential stages of increased severity mixing allow atomization of the liquid into fine droplets with a reduced pressure drop across the discharge nozzles. In a highly preferred form, the liquid injector includes provisions for injecting two fluid streams into a suspension of fluidized solids at two discrete locations.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of prior copendingapplication Ser. No. 005,044 which was filed on Jan. 16, 1987 (now U.S.Pat. No. 4,861,459 issued Aug. 29, 1989) which is a continuation-in-partof prior application Ser. No. 712,298, filed Mar. 15, 1985, and nowabandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the dispersing of liquids intofluidized solids. More specifically this invention relates to a methodand apparatus for atomizing liquid into fine droplets and dispersing thedroplets into a suspension of fluidized solids. A specific aspect ofthis invention relates to the contacting of fluidized catalyst particleswith a liquid hydrocarbon wherein the liquid hydrocarbon is atomizedinto a dispersion of fine droplets to improve the contact between thehydrocarbon and catalyst.

2. Description of the Prior Art

It has been a long recognized objective in the dispersal of fluidstreams into fluid particle suspensions to deliver the liquid in smalldroplets. The small droplets increase interaction between the liquid andsolid. Catalytic conversion of hydrocarbon streams using a fluidizedstream of solid catalyst particles poses a typical example where smalldroplets are needed. Preferably, in hydrocarbon conversion droplet sizesbecome small enough to permit vaporization of the liquid before itcontacts the solids.

It is well known that agitation or shearing can atomize a liquidhydrocarbon feed into fine droplets which are then directed at thefluidized solid particles. A variety of methods are known for shearingsuch liquid streams into fine droplets.

U.S. Pat. No. 3,071,540 discloses a feed injection apparatus for a fluidcatalytic cracking unit wherein a high velocity stream of gas, in thiscase steam, converges around the stream of oil upstream of an orificethrough which the mixture of steam and oil is discharged. Initial impactof the steam with the oil stream and subsequent discharge through theorifice atomizes the liquid oil into a dispersion of fine droplets whichcontact a stream of coaxially flowing catalyst particles.

U.S. Pat. No. 4,434,049 issued to Dean et al. shows a device forinjecting a fine dispersion of oil droplets into a fluidized catalyststream wherein the oil is first discharged through an orifice onto animpact member located within a mixing tube. The mixing tube delivers across flow of steam which simultaneously contacts the liquid. Combinedflow of oil and steam exit the conduit through an orifice which atomizesthe feed into a dispersion of fine droplets and directs the dispersioninto a stream of flowing catalyst particles.

The injection devices of the '540 and '049 patents rely on relativelyhigh fluid velocities and pressure drops to achieve atomization of theoil into fine droplets. Providing this higher pressure drop burdens thedesign and increases the cost of equipment such as pumps and exchangersthat are typically used to supply liquid and gas to the feed injectiondevice. The need to replace such equipment may greatly increase the costof retrofitting an existing liquid-solid contacting installation withsuch an injection apparatus.

Other methods for atomizing liquid feeds with gaseous materials areshown in U.S. Pat. Nos. 3,152,065 and 3,654,140. FIG. 2 of U.S. Pat. No.3,654,140 issued to Griffel et al. shows an injection device thatimparts a tangential velocity to an oil stream to promote its mixingwith a stream of steam which is injected into the oil outside theinjection device. In U.S. Pat. No. 3,152,065 an injection device adds atangential velocity to an annular stream of oil that flows around acentral conduit. Steam passing through the center conduit contacts theoil at the distal end of injector. Steam and oil then pass through anorifice which further atomizes the oil and distributes it into adispersion of fine droplets. In these devices, the tangential velocityof oil in combination with the expansion of the steam is relied on toprovide the energy for atomizing the oil.

Although not a mixing device per se, U.S. Pat. No. 4,097,243 issued toBartholic shows a feed distributor for FCC units that divides thehydrocarbon feed stream into a number of smaller feed streams. Dividingthe hydrocarbon feed into a number of smaller streams promotes bettermixing between the catalyst and the feed.

U.S. Pat. No. 4,562,046 issued to Hays et al. shows a feed injectionapparatus that can subject at least a portion of the feed to severalstages of mixing. The apparatus of Hays also divides the mixed feed intoa plurality of different streams before it is discharged into contactwith FCC catalyst.

SUMMARY OF THE INVENTION

It is an object of this invention to provide an apparatus for atomizingliquid and dispersing the liquid into a suspension of solid particleswithout excessive pressure drop.

It is a further object of this invention to provide an atomizing anddispersing apparatus that is easily incorporated into existing liquidsolid contacting zones.

These objectives are achieved by combining a liquid and gaseous streamunder conditions of sequentially increased mixing severity prior tointroducing the liquid and gaseous streams into a suspension offluidized particles. More specifically, the liquid and gaseouscomponents are sequentially mixed, first in a mild zone that blends theliquid and gaseous components to a uniform consistency. The liquid andgaseous blend is transported to the next zone in a manner that will notresegregate the components. The next mixing stage is of higher severityin that it vigorously mixes the liquid and gaseous blend by impinging itagainst another contact surface to shear the liquid and promote theformation of fine bubbles within the liquid and gaseous mixture. Thismixture of liquid and finely dispersed bubbles are then dischargedthrough a discharge device and into contact with the solid particles.Discharge through the discharge device allows the bubbles to expandrapidly once outside the device. This expansion thoroughly atomizes theliquid. It has been found that the quantity of gaseous material that isrequired for the injection apparatus can be reduced relative to theamount of gas material that is required in other devices or methods foratomizing and dispersing liquids. In hydrocarbon processes such asfluidized catalytic cracking units, it is highly desirable to reduce theamount of steam that must be added since the steam places additionalload on downstream product condensing facilities.

In one embodiment, this invention is an apparatus for mixing a liquidhydrocarbon feed stream and a gaseous material into contact with FCCcatalyst particles. The apparatus includes a conduit with a partitioninside that divides the interior of the conduit into a first chamber ata first end of the conduit and a second chamber. Means are provided forintroducing the feed and gaseous material into the first chamber wheremeans in the conduit mix the liquid hydrocarbon feed and gaseousmaterial into a well dispersed mixture. Means are also provided forcommunicating the well dispersed mixture from the first chamber to thesecond chamber and dividing the well dispersed mixture into a pluralityof discrete streams. The second chamber includes means for directing theprojection of each of the discrete streams into impingement with animperforate wall section or another of the discrete streams. Means areincluded for transferring the mixture from the second chamber to adischarge device from where the mixture is discharged.

This invention is also directed to an apparatus for contacting a streamof fluidized particles with a finely dispersed liquid. In one aspect,the apparatus comprises a pair of conduits. The first conduit transportsa stream of fluidized particles. The second conduit comprises theapparatus as generally described before which provides means for mixingliquid and gaseous streams under conditions of sequentially increasedmixing severity. The second conduit has a partition defining two axiallyspaced regions. In the first region, means are provided for mild mixingand collectively blending the entire gaseous and liquid stream. Theconduit transports the liquid and gaseous blend in a substantial linearflow path to the second or downstream region. The downstream region hasmeans for vigorously mixing the liquid and gaseous blend into ahomogeneous dispersion of liquid and fine bubbles. At least onedischarge device communicates the downstream region with the interior ofthe first conduit. The discharge device has a restricted area that issufficient to atomize liquid into a dispersion of fine droplets and anorientation that directs the dispersion into contact with the stream offluidized particles flowing through the first conduit.

In another, more limited aspect, this invention is directed to anapparatus for introducing at least two fluid streams into a fluidizedcatalytic cracking riser. The apparatus includes an elongated riserconduit having a downstream end from which catalyst and hydrocarbons aredischarged. A regenerator catalyst supply conduit is connected to theside of the riser conduit and supplies regenerated catalyst to the riserat a point upstream of the outlet end of the riser conduit. A portion ofthe riser conduit common with the intersection of the catalyst supplyconduit forms a catalyst entry section of the riser. An inner conduitprojects into the riser conduit and extends parallel to the center lineof the riser to at least a point downstream of the catalyst entrysection. This inner conduit conveys a stream of liquid hydrocarbons andat least one gaseous component into the riser and is separated by aperforated partition into at least one upstream region and onedownstream region. The upstream region contains means for mildly mixingand collectively blending the hydrocarbons and gaseous componentintroduced therein. The downstream region contains another mixing zoneof increased severity that vigorously mixes and homogenizes thehydrocarbons and gaseous component. One or more discharge deviceslocated at the end of the inner conduit communicate the second regionwith the interior of the riser conduit and have a restricted area foratomizing the hydrocarbons into a dispersion of fine droplets and anorientation that directs the dispersion into contact with the catalyst.An outer conduit coaxially surrounds a downstream portion of the innerconduit and has an outlet end located within the catalyst entry sectionthrough which a second fluid enters the riser conduit.

Other aspects, objects and details of this invention are described inconjunction with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of a liquid injector arranged in accordancewith this invention.

FIG. 2 is a cross-section of the liquid injector taken over Section2--2.

FIG. 3 is a plan view of the liquid injector of FIG. 1 taken in thedirection of View 3--3.

FIG. 4 shows an alternate arrangement for a liquid injector designed inaccordance with this invention.

FIG. 5 is a view of the liquid injector of FIG. 4 taken over Section5--5.

FIG. 6 shows a modified form of the injector of FIG. 4.

FIG. 7 shows the injector of FIG. 6 in a riser conversion zone.

DETAILED DESCRIPTION OF THE INVENTION

In order to disperse a liquid into a dispersion of fine droplets,sufficient energy must be imparted to the liquid in order to break theliquid up into small droplets. The prior art has used an expanding gasor gaseous component such as steam in conjunction with another source ofenergy in order to break up the liquid. This other source of energy canconsist of a high pressure drop for the gas and liquid mixture, or anorthogonal velocity component for the liquid mixture at or near thepoint of initial gas and liquid contact. In those cases where the gasand liquid are mixed and simultaneously discharged at high velocity,additional energy usually in the form of pressure drop must be suppliedto the liquid and gas mixture in order to adequately mix and homogenizethe mixture before discharge or to supply additional energy to make upfor inadequate mixing so that a fine and uniform distribution ofdroplets will still be obtained outside the injector apparatus. It hasbeen discovered that the total pressure drop across a liquid injectorcan be reduced and a good dispersion of fine liquid droplets can beobtained from the discharge outlet of the injector by blending andhomogenizing the liquid of gas sequentially in stages of increasedmixing severity.

As stated previously, liquid injectors designed to distribute adispersion of fine droplets in accordance with this invention rely on agaseous medium to ultimately break up the liquid into fine droplets. Theinjector of this invention is particularly suited for hydrocarbonconversion wherein the liquid will be a stream of hydrocarbons and thegaseous medium will be steam, lighter hydrocarbons, i.e., hydrocarbonsthat have a boiling point substantially less than the boiling point ofthe liquid hydrocarbons, hydrogen, or a combination of the above. Thus,the feed distributor will typically distribute liquid hydrocarbons whichenter the injection device at a temperature below their boiling pointbut at a temperature above the boiling point of the steam or gaseoushydrocarbons that enter the injection device along with the liquid.Whatever the relative composition of the liquid and gaseous components,it is essential that a minimum quantity of gaseous material at leastequal to 0.2 wt. % of the combined liquid and gaseous mixture, iscommingled with the liquid entering the injection device.

As the gaseous medium and liquid, in this case steam and hydrocarbons,enter the piping to the liquid injector apparatus they tend to remainsegregated. By this invention, the steam and hydrocarbon mixture passesthrough the first mild mixing zone which blends the hydrocarbon andsteam mixture into a relatively uniform hydrocarbon and steam stream. Bysubstantially uniform, it is meant that any major segregation betweenthe liquid and gaseous component that would tend to deliver more liquidor gaseous medium to one section or another of the subsequent mixingstage have been eliminated. Since this blending is usually mild, thepressure drop across this zone will not normally exceed 10 psi.

The liquid and gaseous mixture is then conveyed, in a manner that willnot resegregate the liquid and gasous components, to at least one moremixing stage that more vigorously mixes the liquid and gas into ahomogeneous mixture of liquid with finely distributed bubbles of thegaseous medium throughout the liquid. The last stage of mixing will usea series of orifices to divide the liquid and gas blend into amultiplicity of streams and initiate the gas dispersion by impactingthis stream with an impact medium. In order to achieve a more vigorousmixing, this stage will usually require a higher pressure drop than theprevious stage. Nonetheless, total pressure drop through this stage willnot normally exceed 20 psi. In the case of oil and steam, thishomogeneous mixture will approach the form of an emulsion.

The homogeneous mixture of liquid and finely dispersed gas bubbles passthrough one or more discharge devices as it exits the injector. Thedischarge devices at least direct the flow of liquid and the gaseousmedium, and can also be designed to increase dispersion of the gaseousmedium. Thus, suitable discharge devices range from simple orifice holesor pipe nozzles to commercially designed spray nozzles. As the liquidand gas leave the discharge devices, bubbles rapidly expand to break upthe surrounding liquid into a dispersion of fine droplets which retainthe trajectory imparted to the liquid as it left the discharge devices.The formed droplets become interspersed with solid particles that aresuspended about the outlet of the injection device.

A specific injector device for providing the sequential stages ofincreased severity mixing is shown in FIG. 1. The injector device ofFIG. 1 is particularly suited for fluid catalytic cracking units whereinhydrocarbons are cracked in the presence of finely divided or fluidizedcatalyst particles. The feed injector device will be further describedin the context of a fluidized catalytic cracking unit, however, thoseskilled in the art will recognize that this invention could findapplication in various liquid and solid contacting processes orapplications.

Focusing then on FIG. 1, the configuration of the feed injector 10conforms to the readily recognizable appearance of an FCC feeddistributor located at the bottom of a riser. Although FIG. 1 shows thefeed injector positioned at the bottom of the riser, feed injectorplacement is not limited to a bottom riser location. The injector may belocated at various points along the length of the riser and may enterthe riser through its sidewall as the bottom. The feed distributor 10has an inner conduit 12 located in the riser conduit 14. Riser conduit14 defines a riser conversion zone 16 wherein solid particles in theform of FCC catalyst are fluidized. External conduit 18 extends outsideriser conduit 14. In this case, distributor 10 also includes aT-junction 20 located upstream of external conduit 18.

Liquid hydrocarbons and a gas medium, in this case steam, enterT-junction 20 through inlet 22. The hydrocarbon is commingled with thesteam in a quantity equal to 0.2 to 5 wt. % of the liquid hydrocarbon,with 0.5 to 2 wt. % being a preferred steam concentration. T-junction 20serves as a first mild mixing zone for blending the commingledhydrocarbon and steam into a relatively uniform mixture. Blending isaccomplished by the flow discontinuity of T-junction 20 which forhydrocarbon and steam mixtures entering the T at velocities greater than30 ft/sec will introduce sufficient turbulence to accomplish the desiredblending. The configuration of the T-junction also serves the importantobjective of collectively blending the entire flow of hydrocarbons andsteam that are charged to injector 10. Collective blending, as opposedto dividing and mixing the stream, is essential so that no localizedvariation of hydrocarbon and steam occurs in the mixture as it leavesjunction 20. The mild mixing that takes place in the T-junction pressuredrop will usually not exceed 5 psi.

As the hydrocarbon and steam mixture moves up through conduit 18 andinto upstream chamber 24, it remains a substantially uniform blend. Thehydrocarbon and steam mixture enters chamber 24 by passing through anorifice plate 19. Orifice plate 19 directs the mixture into impingementwith a partition 26 thereby providing another stage of mild mixing.Chamber 24 is bordered on its top side by a partition 26 having openings28 which lead to the next stage of mixing. It is essential that the oiland gas blend be transferred from the mild mixing stage or stages, inthis case T-junction 20 and orifice plate 19, to the succeeding stage orstages of vigorous mixing in substantially axial or unidirectional flow.Axial or unidirectional flow primarily means that bends or obstructions,serving to introduce tangential velocities, to the hydrocarbon and steamblend should be avoided. Tangential velocities imparted to the entirehydrocarbon and steam blend serve to resegregate the hydrocarbon andsteam. If resegregation occurs, the resulting maldistribution maydeliver different ratios of hydrocarbon and steam to the differentopenings 28. Such a maldistribution can interfere with mixing in thesubsequent mixing stage. The arrangement of injector 10 avoidsresegregation by providing a linear flow path between T-junction 20 andpartition 26. It should be noted that substantially axial flow is onlymeant to prohibit asymetric flow arrangements between the mild mixingzone and subsequent stages of mixing. In the arrangement of distributor10, the expansion of chamber 24 relative to the interior conduit 18 andthe off center location of openings 28 do not promote resegregation butintroduce additional turbulence that further mixes the hydrocarbon andsteam blend. Although orifice plate 19 and T-section 20 providedistributor 10 with two zones of mild mixing, either the T-section ororifice plate by itself can provide adequate mild mixing.

The hydrocarbon and gas mixture passes through openings 28 into the nextzone of mixing. The next zone of mixing consists of mixing caps 30 andthe jets produced by fluid passing through slots 32 which are defined bycaps 30. Mixing caps 30 are located in a downstream chamber 34. FIG. 2depicts at plan view of mixing caps 30 positioned over each of openings28 and the arrangement of slots 32. Each of slots 32 is orientated witha projection that intersects the projection of a corresponding slot on adifferent cap 30. As a portion of the hydrocarbon and steam blend flowsinto one of caps 30 and a yet smaller portion flows out of one of slots32, it impacts with another portion of the hydrocarbon and steam blendthat is discharged from a slot having an intersecting projectiontherewith. In this fashion, the intersecting projections of the slot andthe hydrocarbon and steam flowing therethrough create an impact zone.This impact zone vigorously mixes the hydrocarbon and steam blend todivide the steam and shears the liquid into a homogeneous distributionof liquid and microbubbles. Although in this case, impingement of thehydrocarbon liquid upon itself is the vehicle of vigorous mixing, asequential increase of mixing severity may be accomplished by any meansthat will shear the liquid component of the mixture and divide thegaseous component of the mixture. Multiple slots 32 also encourage thedispersion of the steam into the oil by breaking the mixture into aseries of smaller streams. Slots 32 are designed for an exit velocity ofhydrocarbons and steam of about 50 feet per second. Passage of thegaseous component and liquid through the mixing zone at thebeforementioned velocities produces a total pressure drop ofapproximately 10 psi.

Once the hydrocarbon and steam mixture has gone through the sequentialstages of mixing provided by T-junction 20, plate 19 and caps 30, mixingand homogenation of the mixture is essentially complete and it isdischarged through discharge device, comprising discharge nozzles 36,which communicate chamber 34 with riser conversion zone 16. Although theturbulence associated with passing the hydrocarbon and steam mixture tothe upper portion of chamber 4 and redirection of the mixture intodischarge nozzles 36 could provide further mixing, additional mixingafter the impact zone is usually not beneficial. The most likely resultof such further mixing is coalescence of the microbubbles into largerbubbles prior to their exit through nozzles 36. Any increase in the sizeof the bubbles decreases the degree of atomization of the liquid as itis discharged through nozzle 36. Therefore, it is advantageous to designchamber 34 such that it minimizes residence time for the hydrocarbonsand steam passing therethrough and minimizes mixing between the vigorousmixing zone and discharge nozzles 36.

Discharge nozzles 36 comprise a discharge zone which serves dualpurposes of atomizing the liquid and directing the liquid droplets overriser conversion zone 16. FIG. 3 depicts nozzles 36 in a directionallyorientated array that collectively have a reduced cross-sectional arearelative to a cross-section of chamber 34. The reduced area of thenozzles offers a flow restriction that increases the flow velocity ofthe fluid exiting the nozzles. Subsequent expansion of the microbubblespresent in the hydrocarbon and steam mixture atomizes the liquid as itpasses out of the nozzles 36. Typically, passage of the liquid and gasmixture through the discharge zone imposes a pressure drop of about 20to 40 psi. This pressure drop is considerably less than the pressuredrop that would be required to completely atomize the oil if the gaseousmedium was not highly dispersed throughout the oil by the sequentialstages of mixing hereinbefore described. Velocity of the hydrocarbon andsteam mixture leaving the nozzles is in the range of about 50 to 125feet per second with a velocity in the range of 75 to 100 feet persecond being preferred. This range of velocities contrast sharply withother atomizing devices which need exit velocities in the range of 200ft/sec or higher for good atomization. A lower velocity is preferredsince it requires less pressure drop. In addition, high velocity jetsimpart momentum to the solids which are contacted thereby. The momentumcauses additional collisions between the solid particles and leads toattrition damage of the solid particles as well as erosion damage to theequipment. The lower range of velocities hereinbefore mentioned ispreferred because it avoids such damage while still imparting sufficientmomentum to the fluid to provide a good distribution of the dropletsover a wide area of solids.

It is readily understood from the foregoing description that the degreeof atomization or the size of droplets formed is to a large extentdependent on the amount of pressure drop that can be tolerated throughthe sequential mixing stages and the discharge zone. Therefore, whilethis distributor has been designed to operate at lower pressure dropsand with reduced amounts of gaseous medium, the pressure drop and or theamount of gaseous medium can be increased to achieve any increaseddegree of atomization that is required.

FIG. 4 illustrates an alternate arrangement for a feed distributor ofthis invention having a mild mixing zone and a vigorous mixing zone thatdiffer from those shown in FIG. 1. A liquid injector 50 as shown in FIG.4, has a continuous conduit 52 that extends into the interior of a riserconduit 54. A partition 56 divides the interior of conduit 52 into anupstream region 58 and a downstream region 60. A mixing conduit 62pierces partition 56 and projects into upstream region 58 and downstreamregion 60. As commingled hydrocarbon and steam enter upstream region 58,it is communicated to the interior of mixing conduit 62 through a seriesof large apertures 64 defined by the upstream extension of mixingconduit 62. The series of apertures 64 consist of one aperture in abottom closure plate 66 and a number of equally spaced apertures locatedabout the side wall of conduit 62. Apertures 64 have inwardly convergingprojections that intersect at a common point and direct all of thehydrocarbon and steam mixture entering conduit 62 into a commoncollection point to blend the hydrocarbon and steam mixture and providea zone of mild mixing. The blended mixture of hydrocarbon and steamflows out of conduit 62 through a series of small apertures 68 whichdivide the mixture into a multiplicity of smaller streams that initiatedispersion of the steam through the oil. Apertures 68 direct thehydrocarbon and gas mixture into an impingement with an impact mediumwhich in this case consists of the imperforate portions of a perforatedcylindrical tube 70. Together the holes 68, defined by conduit 62, andtube 70 provide a zone of vigorous mixing in the form of an impingementarea. As shown in FIG. 5, the perforations 72 of tube 70 do not coincidewith aperture 68. Therefore apertures 68 direct the mixture ofhydrocarbon and steam into imperforate portions of tube 70. Impact ofthe hydrocarbon and steam mixture with the tube wall again shears theliquid and breaks up the steam into a dispersion of microbubblesthroughout the liquid hydrocarbon. The perforations of tube 70 have agreater open area than the apertures of 68 so that hydrocarbons and gaspassing through perforation 72 will not impact the interior of conduit52 with substantial momentum. The homogenized mixture of hydrocarbonsand steam passing out of apertures 68 flows upwardly through annularregions to either side of tube 70 and into downstream chamber 60.Hydrocarbons and gas pass through downstream chamber 60 and outdischarge nozzles 74 which again atomize and distribute the dispersionof fine droplets as hereinbefore described.

In this arrangement, sequential mixing of increased severity is providedprincipally by a single mixing conduit. In and out flow through theconduit conveniently provides collective mixing for blending the entireflow of hydrocarbon and steam and impingement for increased severitymixing. The single mixing conduit allows sequential mixing to beachieved with a relatively small amount of hardware. As a result, allthe mixing can be achieved in that portion of the injector that islocated within the riser conversion zone.

In a highly preferred embodiment, the liquid injection apparatus of thisinvention includes provision for injecting fluids into the riserconversion zone at two discrete locations. FIG. 6 illustrates a modifiedinjector 100 that incorporates an annular conduit 102 for receivinganother fluid such as a secondary feed or fluidizing medium through aset of inlet nozzles 104. Fluid entering through nozzles 104 isdischarged through secondary outlets 106 at a location below ordownstream outlets 74 of conduit 52. Preferably, the fluid enteringnozzles 104 is a hydrocarbon and gaseous mixture. An annular area 108defined by annular conduit 102 and conduit 52 contains flow devices foragain dispersing the liquid hydrocarbon into fine droplets. As the fluidenters annular area 108, bayonet ends 110 of nozzles 104 direct fluidlaterally through a series of holes 112 to mix liquid and gaseouscomponents. The mixed liquid and gaseous components pass through anorifice 114, at the inlet of nozzle 106 which atomizes the liquid intodroplets before it passes out of nozzle 106. When a mixed phase streamof liquid and gaseous material enters nozzle 104, it usually has a muchhigher concentration of gaseous material to liquid than the liquid andgaseous material entering conduit 52.

The operation of the injector of FIG. 6 can be more fully appreciated inconjunction with the operation of an FCC riser. FIG. 7 shows theinjector of FIG. 6 in an FCC riser conversion zone. The conversion zonehas a reactor riser conduit 116 containing the injector 100, and aregenerated catalyst conduit 118 having a catalyst flow control valve119. As the process is carried out, regenerated catalyst from conduit118 first contacts the fluid entering the riser conversion zone viaoutlets 106. As this first fluid and catalyst mixture ascends upward orupstream, it is contacted with a feed entering from discharge nozzles74. Both process streams and the catalyst continues upward through riser1 until it is discharged into a disengaging vessel (not shown) at theupper end of the riser.

The relative location of discharge nozzles 74 and outlets 106 withrespect to the opening of the catalyst conduit is an important featureof this embodiment. The intersection of the catalyst conduit and theriser conduit define a catalyst entry section which is bounded on theupper or downstream side by dashed line A and on its lower or upstreamside by dashed line B, with both lines having a perpendicularorientation to the riser centerline. (For convenience the boundaries ofcatalyst entry section and conduit openings will be described by theterms upper or lower and above or below, the usage of which is not meantto limit the riser to a vertical configuration). Initial accelerationand fluidization of the catalyst is primarily accomplished by fluidentering through the outlets 106. At the location of initial catalystcontact with the fluid, there is a great deal of turbulence andbackmixing that occurs. Backmixing will adversely affect reactions inthe riser resulting in overcracking and undesirable reaction products.Turbulent conditions also greatly accelerate erosion of equipment due tothe abrasive nature of FCC catalyst. By performing this initial mixingwith fluid entering through the outlets 106, a hydrocarbon feed may beadded through the nozzles 74 so that the adverse effects of theturbulence and backmixing may be eliminated or minimized with respect tothe feed entering thereby.

The disadvantages associated with poor initial catalyst mixing may beeliminated by injecting a fluidizing medium into the riser conduitthrough nozzles 106. This will allow the catalyst to achieve a moreuniform flow profile before contacting a feed which is introducedthrough the nozzles 74. Suitable fluidizing mediums include steam, lightgaseous hydrocarbons or feedstocks requiring longer residence times orincreased catalyst activity. From the standpoint of fluidization, theintroduction of a fluidizing medium in the manner of this invention willeliminate erosion that has been associated with the addition offluidizing medium in other locations of the riser. The location of theoutlets 106 within the region of the standpipe opening takes the highturbulence associated with initial mixing out of the extreme upstreamend of the riser thereby minimizing the potential for erosion in thiszone. In the past, steam or other gaseous mediums were injected in thelowermost portion of the riser to provide additional fluidization to thecatalyst entering the riser. However, injecting steam in the bottomportion of the riser results in erosion of pipes, nozzles and othercomponents located in the lowermost portion of the riser. While it ispossible to inject fluidizing medium at a more downstream locationwithin the riser, i.e., below the catalyst entry section by means ofpipe extensions from the riser end enclosure or nozzles inserted intothe side of the riser, these methods interfere with the flow path of thecatalyst over the riser cross-section and place additional pipecomponents, which are subject to erosion, within the path of the movingcatalyst. Conversely, by the apparatus of this invention, fluidizingmedium can be added to a downstream location within the riser withoutthe use of pipe extensions or additional inlet nozzles in the side ofthe riser.

The lower portion of the riser is extremely susceptible to erosion dueto the dissipation of downward particle momentum that occurs in thisregion. Effecting a major addition of fluidizing medium in the catalystentry section reduces turbulence by allowing mixing in a less confinedregion of the riser. Moreover, turbulence is further reduced sincedownward momentum of the catalyst is dissipated in a layer of relativelystagnant catalyst which forms below outlets 106. Therefore, for purposesof minimizing erosion, the preferred location for the outer conduitoutlet is at or above the midpoint of the catalyst conduit opening whichis defined by the intersection of catalyst conduit centerline C with theprojection of riser wall as given by line D (see FIG. 7).

The limitation on the downstream location of the outlets 106, i.e.,below line A, minimizes the requirements of fluidizing medium. If theoutlets were located above the catalyst entry section, it would benecessary to greatly increase the volume of fluidizing medium in orderto provide the lift necessary to transport the catalyst away from theopening of the catalyst entry section.

Nozzles 74 are above the catalyst entry section, i.e., at or above lineA. Therefore, the feed entering the riser through the nozzles 74 will beat a point downstream of the outlets 106. Factors affecting thedownstream location of nozzles 74 are: the necessary riser residencetime for the feed entering through nozzles 74; the overall length of thefeed injector; and the provision of an adequate distance between outlets106 and nozzles 74 such that fluidizing medium entering through outlets106 can distribute and evenly disperse the catalyst into a dilute phasebefore the catalyst reaches nozzles 74.

An additional advantage of using an injector capable of adding feeds attwo locations is the possibility of adding feedstocks having differentproperties. Suitable feedstocks for outlets 106 would be those requiringincreased catalyst activity or contact time to effect the desirablecracking reactions or those feed components where a separate crackingzone is desirable. Examples of hydrocarbons for this purpose arestraight run or cracked naphthas, or paraffinic raffinates. Similarly,light hydrocarbons may be added at this point to effect passivation ofthe catalyst as taught in U.S. Pat. No. 4,479,870. Thus, this inventionalso allows a dual function lift gas to be introduced into the risersection in a highly effective manner.

What is claimed is:
 1. An apparatus for mixing a liquid hydrocarbon anda gaseous material and discharging the mixture into contact with FCCcatalyst particles, said apparatus comprising:(a) a conduit having firstand second ends; (b) a partition in said conduit dividing the interiorof said conduit into a first chamber located at said first end of saidconduit and a second chamber; (c) means for introducing said hydrocarbonand gaseous material into said first chamber; (d) means in said conduitfor mixing said hydrocarbon and said gaseous material upstream of saidsecond chamber and forming a well dispersed mixture; (e) means forcommunicating said well dispersed mixture from said first chamber tosaid second chamber and dividing said well dispersed mixture into aplurality of discrete streams; (f) means in said second chamber fordirecting the projection of each of said discrete streams intoimpingement with an impact medium, said impact medium comprising atleast one of an imperforate wall section and another of said discretestreams; (g) a discharge device at the second end of said conduitdefining a plurality of openings that define a restricted flow area; and(h) means for transferring said mixture from said second chamber to saiddischarge device through said plurality of openings that define saidrestrictive flow area.
 2. The apparatus of claim 1 wherein said conduitincludes a T-junction which define said means for mixing upstream ofsaid second chamber.
 3. The apparatus of claim 1 wherein said partitionhas a plurality of holes which define said means for communicating saidwell dispersed mixture from said first chamber to said second chamberand dividing said well dispersed mixture into a plurality of discretestreams.
 4. The apparatus of claim 3 wherein a plurality of pipesections are fixed to said partition to subdivide said plurality ofdiscrete streams and define said means for directing said discretestreams into impingement with another of said streams.
 5. The apparatusof claim 1 wherein said partition includes a pipe section having an openinterior which define said means for communicating said well dispersedmixture from said first chamber to said second chamber, a section ofsaid pipe extends into said second chamber, said section of pipeextending into said second chamber has a plurality of circumferentiallyspaced openings through the wall of said pipe which define said meansfor dividing said mixture into a plurality of discrete streams and saidmeans for directing the projection of each of said discrete streams. 6.The apparatus of claim 5 wherein a cylindrical member surrounds saidsection of pipe which define said imperforate wall sections.
 7. Theapparatus of claim 1 wherein said plurality of openings in saiddischarge device are defined by a plurality of pipe nozzles. 8.Apparatus for contacting a stream of fluidized particles with a liquidhydrocarbon and a gaseous material, said apparatus comprising:(a) afirst conduit for transporting a stream of fluidized particles; (b) asecond conduit extending at least partially into said first conduit,said second conduit having a first end that receives said hydrocarbonand gaseous material and a second end that disperses said hydrocarbonand gaseous material into said second conduit; (c) at least onepartition for dividing said second conduit into at least one upstreamchamber in direct communication with said first end of said secondconduit and one downstream chamber in direct communication with saidsecond end of said second conduit, said partition having at least oneopening for communicating said upstream chamber with said downstreamchamber; (d) means in said upstream chamber for mixing said hydrocarbonand gaseous material; (e) means for communicating said hydrocarbons andgaseous material from said upstream chamber to said downstream chamberand means in said downstream chamber for dividing said hydrocarbon andgaseous material into a plurality of discrete streams and directing theprojection of each of said discrete streams into impingement with animpact medium, said impact medium comprising at least one of animperforate wall section and another of said discrete streams; (f) atleast one discharge device having a plurality of restricted openingscommunicating the end of said downstream chamber with the interior ofsaid first conduit, said discharge device having a restricted areasufficient to atomize said liquid into a dispersion of fine droplets andan orientation that directs said dispersion into contact with saidstream of fluidized particles; and (g) means for transferringhydrocarbons and gaseous materials from the downstream chamber to thedischarge device through said plurality of openings that define saidrestrictive flow area.
 9. The apparatus of claim 8 wherein said meansfor mixing includes a 90° bend formed by a T-junction in said conduit.10. The apparatus of claim 8 wherein an annular distributor forintroducing a fluid into the interior of said first conduit surrounds aportion of said second conduit that extends into said first conduit,said annular distributor having at least one outlet communicating theinterior of said distributor with the interior of said first conduit.11. The apparatus of claim 10 wherein said distributor includes meansfor mixing and atomizing said fluid before it enters said first conduit.12. The apparatus of claim 8 wherein said means for mixing in saidupstream chamber and said means for dividing in said downstream chambersincludes a third conduit, said third conduit defining a series of inletapertures communicating the interior of said third conduit with saidupstream chamber, said inlet apertures having inwardly convergingprojections that combine the hydrocarbon and gaseous material, and aseries of outlet apertures having outwardly diverging projectionscommunicating the interior of said third conduit with the interior ofsaid downstream chamber.